In the United States, the government has allocated three ranges or bands in the electromagnetic radio spectrum for television broadcast and reception. These are from 54 to 88 megahertz (MHz), from 174 to 216 MHz, and from 470 to 890 MHz. These ranges or bands are further divided into individual channels, each being 6 MHz wide. There are thus five channels in the first band, seven in the second, and seventy in the third band. By convention also, the lowest frequency channel, that is from 54 to 60 MHz, is designated channel 2 while each progressively higher channel frequency is designated by the next highest number. Thus, channels 2-6 are in the first band, channels 7-13 in the second band and channels 14-83 in the third band.
The lower two bands (channels 2-13), despite the gap between them, are conventionally referred to as a single band, namely, the Very High Frequency or VHF band. The other band (channels 14-83) is referred to as the Ultra High Frequency or UHF band.
Because of the great disparity between the VHF and UHF frequency ranges, it is the normal practice to employ two separate tuners in a television set designed to receive the VHF and UHF bands. Recently, solid-state tuners have been developed which tune to desired frequencies or channels in response to the application of voltages of various levels. Examples of such tuners are disclosed in Wittig U.S. Pat. No. 3,354,397 and Manicki U.S. Pat. No. 3,643,168.
The requirement imposed by the government that each television set sold in the United States be capable of tuning to all possible channels has presented difficulties with regard to the construction of inexpensive, durable and compact controls for use with the solid-state tuner circuitry. Adding to the difficulties encountered are factors which include the desirability of providing a single tuner control having the capability of selecting both VHF and UHF channels, of providing a control affording preset fine tuning, and providing a control presenting the rotary detent type of channel selection which television viewers are accustomed to.